Touch-responsive tone envelope control circuit for electronic musical instruments

ABSTRACT

In a keying system for an electronic musical instrument in which an individual keyer is controlled in response to the intensity of depression of a corresponding playing key so that a keyed tone signal has an amplitude in accordance with the key depression intensity, there are further provided impedance converter circuits for providing keying signals of low output impedance and waveform-shaping circuits for converting the keyed tone signal into a required waveform each corresponding in number to the number of the keyers. The arrangement enables each of the tone keyers to be of a low impedance so that the individual keyer is easily connected with the corresponding waveform-shaping circuit resulting in prevention of unwanted inductive interferences.

United States Patent 3,567,839 3/1971 Dijksterhuis................. 3,582,530 6/1971 [72] Inventor RyuI-Iiyama 84/l.26 84/l.1 84/1.l3

Adachi............... 3,248,470 4/1966 Markowitzet al.. 3,553,337 1/1971 Dijksterhuis.................

FOREIGN PATENTS 9/1969 GreatBritain................

Primary Examiner- Lewis 1-! Myers Hamamatsu, Japan [21] Appl. No. 60,280 [22] Filed Aug. 3, 1970 [45] Patented Jan. 11, 1972 Assistant Examiner-Stanley J. Witkowski Attorney--Cushman, Darby & Cushman ABSTRACT: In a keying system for an electronic musical instrument in which an individual ke to the intensity of depression of so that a keyed tone signal has [73] Assignee Nippon Gakki Seizo Kabushiki Kaisha Hamamatsu-shi, Japan [32] Priority Aug. 5, 1969 [33] Japan [31 44/74358 TOUCH-RESPONSIVE TONE ENVELOPE yer is controlled in response CONTROL CIRCUIT FOR ELECTRONIC MUSICAL INSTRUMENTS a corresponding playing key an amplitude in accordance y, there are further provided 5 Claims, 5 Drawing Figs.

with the key depression intensit f ommm S licee mrmh m 1 1 m m aw dm gnwt. Wif

"m uo .l qr. V ee O b m r aw impedance converter circuits fo low output impedance and wave verting the keyed tone signal into a corresponding in number to the num rangement enables each of the tone pedance so that the individual ke the corresponding waveform 1 1 94 L DJ H111 1 MM .1 2 a m m MG m m m D m m 7. m mmG HUI "mD m mm6 ""2 u m mh "c 1 l a u "e n "S d 5 L4. U .mF .1] 2 0 5 55 .l [1.

keyers to be of a low imyer is easily connected with -shaping circuit resulting in prevention of unwanted inductive interferences.

[56] References Cited UNITED STATES PATENTS Re27,015 12/1970 Dijksterhuis et a1.

T- TA I 1 I L BACKGROUND OF THE INVENTION The present invention relates generally to electronic musical instruments, and more particularly to a touch-responsive tone envelope control circuit for improving the tonal effects in a key-operated electronic musical instrument such as an electronic musical organ.

Therefore, the principal object of the present invention is to provide a specific tone envelope control circuit for an electronic musical instrument to provide excellent effects of music being played.

Another object of the present invention is to provide a tone envelope control circuit for an electronic musical instrument minimizing inductive interferences therein and providing a keyed tone signal having an amplitude in accordance with a key depression intensity.

A further object of the present invention is to provide a tone envelope control circuit permitting generation of a sawtooth wave tone signal which is simple in construction and reliable in operation and inexpensive to manufacture.

Other objects, features and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT Description will be made to an embodiment of the present invention with reference to the drawings.

Referring now to FIG. 1, L designates a coil directly grounded at one end thereof and adapted to vary the interlinking fluxes in association with the depression of a playing key K arranged on a keyboard of an electronic musical instrument, e.g., the key carrying a magnet thereunder, and the other end of said coil being grounded through a series circuit of a rectifying element D and a capacitor C. A junction d between the element D and the capacitor C is connected to a movable contact of a key-operated normally closed switch S which is actuated in association with the operation of the corresponding key K. A stationary contact of the switch S is grounded through a resistor R. Thus, the above-mentioned entire arrangement is shown as a key-depressing speed-detecting circuit KS which is indicated in a block.

The junction point d is connected, through a resistor R,, to the gate of a field effect transistor 0,, (hereunder referred to as an FET Q) which constitutes a source follower in an impedance converter circuit Z. The source of the FET Q, is connected via a resistor R to the base of an emitter-grounded transistor 0,. The collector of the transistor Q, is connected via a resistor R to a connection point d, of a diode D, included in a tone signal keyer circuit SA (shown in block) having therein a waveform-shaping circuit. The other connection point d of the diode D, is connected to another diode D connected in series with the diode D,. The other end pole of the diode D is connected via a resistor R to an intermediate output terminal T, which is grounded via a parallel circuit of a rewave out of an input square wave. The juncture (1;, is connected through a resistance element R to a power supply +Vcc, while the juncture d, of the diode D, is connected through a capacitor C, and a series-connected resistor R to a tone signal input terminal t,.

A further tone signal input terminal t is connected, via a further tone signal-keying and wavefonn-shaping circuit SA, (shown in block) and another amplifier A,, to another terminated output terminal TB, and the juncture r between a resistor R and a capacitor C,,, a coil L, and a resistor R are connected to another intermediate output terminal T Now, it should be noted that the resistors without reference numerals are those for load elements and bias application elements for the transistors 0,, Q and Q11, and the FET 0 Further, in the normal state at which no key depression is effected, the transistor Q, is in its cutoff state and the collector potential thereof is rendered more positive than DC potentials at the respective junction d and (1, so that the diodes D,, D,, D,, and D constituting keyers are reverse biased to be in their cutoff states respectively. By making use of these diodes D,, D D,, and D tone input signals of different footages (e.g., an 8-foot signal and a 4-foot signal) applied to the input terminals t, and t are thus cut off. The number of each of the above-mentioned circuits KS, Z, SA, SA,, A and A, which are installed in the console of the electronic musical instrument corresponds in number to the playing keys, for example, 61

Now, description will be made on the operation of the above-mentioned circuit arrangement.

At first, when any one key K provided in the instrument is depressed, a magnetic member-which may be either magnetized or not magnetized and which may be attached to the key-moves toward or away from the fixed coil L, thereby resulting in a damped pulse voltage-which is approximately proportional to the intensity or the speed of depression of the playing key-due to variation in interlinking fluxes established around the coil, as shown by a waveform in FIG. 2a. The induced alternative voltage is rectified through the diode D and as a result, positive DC components developed at the diode D are stored in the capacitor C. The positive charge stored on the capacitor C may be used so that the drain-source impedance of the FET Q, is caused to be varied (lowered) in response to the gate input levels thereof, i.e., the key depression intensity. Accordingly, the source potential of the F ET Q, may also be raised in accordance with the intensity of the key depression, and hence, the collector potential of the transistor Q, is lowered in accordance with the key depression intensity as shown by a waveform in FIG. 2b. This results in conduction of the diodes D,, D D,, and D,,, of the circuits SA and 8A,, which respectively have impedances associated with the key depression intensity at that time. Then, the input tone signals of different footages applied to the tone input terminals t, and as shown by a waveform in FIG. 3a, are keyed by the respective keying diodes D,, D,, D,, and D,, and then are subjected to waveform shaping by respective circuits including capacitors C and C (together with diode D and capacitors C and C,., (together with diode D,,.) respectively, thereby resulting in sawtooth wave signals at their output terminals T, and T as shown by a waveform in FIG. 3b. The respective output sawtooth wave signals may be derived which have different footages to each other and levels corresponding to the key depression intensity. Thus, the present arrangement permits a tone envelope control which provides a so-called touchresponsive effect in an electronic musical instrument.

Further, when the above-mentioned output signals as shown in FIG. 3b are subjected to amplitude amplification by the amplifiers A and A,, respectively, the signals thus amplified can be derived at the last stage output terminals TA and TB separately.

In the case described above, if the playing key K is kept depressed, no further voltage is induced in the coil L. However, since the input gate impedance of the FET Q,, is greatly high, for example, 10 ohms, the charge stored on the capacitor C immediately after depression of the key has no discharging path with the switch S opened, and accordingly, it does not discharge for a long period of time, so that the FET Q, is held in its conducting states during the key depression, and accordingly, the collector potential of the transistor is also kept lowered as shown in FIG. 2b. This causes the diodes D,, D D, and D to be forward biased to be conductive, at each of terminals T T and TA and TB continuously providing the output tone signal having a level responsive to the key depression intensity.

Then, upon release of the key being depressed, the key is made restored by its self-return action and simultaneously, the switch S is closed, so that the charge stored on the capacitor C discharges in a short period of time through the resistor R having a relatively low resistance. As a result, the source potential of the FET 0,, becomes the ground potential, i.e., zero volts to render the transistor Q in its nonconducting state, so that the collector potential of the transistor Q becomes close to the voltage of the power source +Vcc. As a result, the diodes D,, D D and D are no longer forward biased to be rendered in their nonconducting states, so that no output signal is developed at any of output terminals T T TA and TB.

As described above, in the present invention, a low-impedance circuit constituted by low-impedance switching elements such as diodes may easily controlled directly by varying the collector potential of a usual transistor under a condition of its low impedance. This permits even simplified construction of the tone signal keying and waveform-shaping circuits to function stably. Further, since the transmission circuits of the tone signals as described above have low impedances no inductive interference due to external undesired noises is encountered. Thus, the present invention makes it possible to provide a touch-responsive tone envelope control circuit which is good in quality and not expensive and can easily provide tone signals of sawtooth waves having all harmonics and levels responsive to the key depression, i.e., so-called touchresponsive tone envelope effects, resulting in a variety of excellent tonal effects for music being played.

As the key depression speed-detecting circuit KS, magnetosensitive elements or pressure-sensitive elements may be used in place of the induction coil used here. Furthermore, the F ET used in the present circuit may be substituted by other switching elements. The diodes D,, D D and D may also be replaced by other nonlinear active elements such as transistors and vacuum tubes or the like.

I claim:

1. In an electronic musical instrument having individual playing keys, a touch-responsive keying system for each playing key, said system comprising:

means associated with a respectively corresponding playing key for generating a damped voltage having an amplitude responsive to the intensity with which said respectively corresponding playing key is depressed;

a charge storage element connected to said means for storing a quantity related to said damped voltage;

an impedance converter circuit having a control terminal presenting a high-input impedance and an output terminal presenting a low-output impedance, said control terminal being connected to said charge storage element; and

a keyer circuit including a switching element connected to the output terminal of said impedance converter circuit whereby the switching element is subject to biasing control for gating a square wave tone signal in accordance with an output from said impedance converter circuit and a waveform converter circuit connected subsequent to said switching element for converting the square wave of the gated tone signal into a sawtooth wave.

2. A touch-responsive keying system as in claim 1, wherein said impedance converter circuit includes:

a first active element having a control electrode exhibiting a high-input impedance and an output electrode,

said control electrode of the first active element being connected to said control terminal of the impedance converter circuit, and a second active element having a control electrode connected to the output electrode of said first active element and having an output electrode exhibiting a low-output impedance connected to said output terminal of the impedance converter circuit.

3. A touch-responsive keying system as in claim 2 wherein said first active element comprises a field effect transistor, said second active element comprises a transistor, and said switching element comprises a diode.

4. A touch-responsive keying system as in claim 1 wherein:

said switching element comprises a first diode,

said waveform converter circuit includes a second diode connected subsequent to said first diode, and two capacitors, one capacitor connected between one pole of said second diode and an electrical ground and the other capacitor connected between the other pole of said second diode and the electrical ground.

5. A touch-responsive keying system as in claim 1 wherein there is further provided a key-operated switch of a normally closed type and a resistor, the switch and the resistor being connected in series across said charge storage element. 

1. In an electronic musical instrument having individual playing keys, a touch-responsive keying system for each playing key, said system comprising: means associated with a respectively corresponding playing key for generating a damped voltage having an amplitude responsive to the intensity with which said respectively corresponding playing key is depressed; a charge storage element connected to said means for storing a quantity related to said damped voltage; an impedance converter circuit having a control terminal presenting a high-input impedance and an output terminal presenting a low-output impedance, said control terminal being connected to said charge storage element; and a keyer circuit including a switching element connected to the output terminal of said impedance converter circuit whereby the switching element is subject to biasing control for gating a square wave tone signal in accordance with an output from said impedance converter circuit and a waveform converter circuit connected subsequent to said switching element for converting the square wave of the gated tone signal into a sawtooth wave.
 2. A touch-responsive keying system as in claim 1, wherein said impedance converter circuit includes: a first active element having a control electrode exhibiting a high-input impedance and an output electrode, said control electrode of the first active element being connected to said control terminal of the impedance converter circuit, and a second active element having a control electrode connected to the output electrode of said first active element and having an output electrode exhibiting a low-output impedance connected to said output terminal of the impedance converter circuit.
 3. A touch-responsive keying system as in claim 2 wherein said first active element comprises a field effect transistor, said second active element comprises a transistor, and said switching element comprises a diode.
 4. A touch-responsive keying system as in claim 1 wherein: said switching element comprises a first diode, said waveform converter circuit includes a second diode connected subsequent to said first diode, and two capacitors, one capacitor connected between one pole of said second diode and an electrical ground and the other capacitor connected between the other pole of said second diode and the electrical ground.
 5. A touch-responsive keying system as in claim 1 wherein there is further provided a key-operated switch of a normally closed type and a resistor, the switch and the resistor being connected in series across said charge storage element. 